chore: get rid of <Browser> templating (#209)

src/browserContext.ts

@@ -18,28 +18,41 @@
 import { assert } from './helper';
 import { Page } from './page';
 import * as network from './network';
+import * as childProcess from 'child_process';
 
-export interface BrowserDelegate<Browser> {
-  contextPages(): Promise<Page<Browser>[]>;
-  createPageInContext(): Promise<Page<Browser>>;
+export interface BrowserInterface {
+  browserContexts(): BrowserContext[];
+  close(): Promise<void>;
+  createIncognitoBrowserContext(): Promise<BrowserContext>;
+  defaultBrowserContext(): BrowserContext;
+  newPage(): Promise<Page>;
+  pages(): Promise<Page[]>;
+  process(): childProcess.ChildProcess | null;
+  version(): Promise<string>;
+  userAgent(): Promise<string>;
+}
+
+export interface BrowserDelegate {
+  contextPages(): Promise<Page[]>;
+  createPageInContext(): Promise<Page>;
   closeContext(): Promise<void>;
   getContextCookies(): Promise<network.NetworkCookie[]>;
   clearContextCookies(): Promise<void>;
   setContextCookies(cookies: network.SetNetworkCookieParam[]): Promise<void>;
 }
 
-export class BrowserContext<Browser> {
-  private readonly _delegate: BrowserDelegate<Browser>;
-  private readonly _browser: Browser;
+export class BrowserContext {
+  private readonly _delegate: BrowserDelegate;
+  private readonly _browser: BrowserInterface;
   private readonly _isIncognito: boolean;
 
-  constructor(delegate: BrowserDelegate<Browser>, browser: Browser, isIncognito: boolean) {
+  constructor(delegate: BrowserDelegate, browser: BrowserInterface, isIncognito: boolean) {
     this._delegate = delegate;
     this._browser = browser;
     this._isIncognito = isIncognito;
   }
 
-  async pages(): Promise<Page<Browser>[]> {
+  async pages(): Promise<Page[]> {
     return this._delegate.contextPages();
   }
 
@@ -47,11 +60,11 @@ export class BrowserContext<Browser> {
     return this._isIncognito;
   }
 
-  async newPage(): Promise<Page<Browser>> {
+  async newPage(): Promise<Page> {
     return this._delegate.createPageInContext();
   }
 
-  browser(): Browser {
+  browser(): BrowserInterface {
     return this._browser;
   }
 

src/chromium/Browser.ts

@@ -19,7 +19,7 @@ import * as childProcess from 'child_process';
 import { EventEmitter } from 'events';
 import { Events } from './events';
 import { assert, helper } from '../helper';
-import { BrowserContext } from '../browserContext';
+import { BrowserContext, BrowserInterface } from '../browserContext';
 import { Connection, ConnectionEvents, CDPSession } from './Connection';
 import { Page } from '../page';
 import { Target } from './Target';
@@ -30,15 +30,15 @@ import { FrameManager } from './FrameManager';
 import * as network from '../network';
 import { Permissions } from './features/permissions';
 
-export class Browser extends EventEmitter {
+export class Browser extends EventEmitter implements BrowserInterface {
   private _ignoreHTTPSErrors: boolean;
   private _defaultViewport: types.Viewport;
   private _process: childProcess.ChildProcess;
   _connection: Connection;
   _client: CDPSession;
   private _closeCallback: () => Promise<void>;
-  private _defaultContext: BrowserContext<Browser>;
-  private _contexts = new Map<string, BrowserContext<Browser>>();
+  private _defaultContext: BrowserContext;
+  private _contexts = new Map<string, BrowserContext>();
   _targets = new Map<string, Target>();
   readonly chromium: Chromium;
 
@@ -80,16 +80,16 @@ export class Browser extends EventEmitter {
     this._client.on('Target.targetInfoChanged', this._targetInfoChanged.bind(this));
   }
 
-  _createBrowserContext(contextId: string | null): BrowserContext<Browser> {
+  _createBrowserContext(contextId: string | null): BrowserContext {
     const isIncognito = !!contextId;
     const context = new BrowserContext({
-      contextPages: async (): Promise<Page<Browser>[]> => {
+      contextPages: async (): Promise<Page[]> => {
         const targets = this._allTargets().filter(target => target.browserContext() === context && target.type() === 'page');
         const pages = await Promise.all(targets.map(target => target.page()));
         return pages.filter(page => !!page);
       },
 
-      createPageInContext: async (): Promise<Page<Browser>> => {
+      createPageInContext: async (): Promise<Page> => {
         const { targetId } = await this._client.send('Target.createTarget', { url: 'about:blank', browserContextId: contextId || undefined });
         const target = this._targets.get(targetId);
         assert(await target._initializedPromise, 'Failed to create target for page');
@@ -127,18 +127,18 @@ export class Browser extends EventEmitter {
     return this._process;
   }
 
-  async createIncognitoBrowserContext(): Promise<BrowserContext<Browser>> {
+  async createIncognitoBrowserContext(): Promise<BrowserContext> {
     const {browserContextId} = await this._client.send('Target.createBrowserContext');
     const context = this._createBrowserContext(browserContextId);
     this._contexts.set(browserContextId, context);
     return context;
   }
 
-  browserContexts(): BrowserContext<Browser>[] {
+  browserContexts(): BrowserContext[] {
     return [this._defaultContext, ...Array.from(this._contexts.values())];
   }
 
-  defaultBrowserContext(): BrowserContext<Browser> {
+  defaultBrowserContext(): BrowserContext {
     return this._defaultContext;
   }
 
@@ -174,11 +174,11 @@ export class Browser extends EventEmitter {
       this.chromium.emit(Events.Chromium.TargetChanged, target);
   }
 
-  async newPage(): Promise<Page<Browser>> {
+  async newPage(): Promise<Page> {
     return this._defaultContext.newPage();
   }
 
-  async _closePage(page: Page<Browser>) {
+  async _closePage(page: Page) {
     await this._client.send('Target.closeTarget', { targetId: Target.fromPage(page)._targetId });
   }
 
@@ -186,7 +186,7 @@ export class Browser extends EventEmitter {
     return Array.from(this._targets.values()).filter(target => target._isInitialized);
   }
 
-  async _activatePage(page: Page<Browser>) {
+  async _activatePage(page: Page) {
     await (page._delegate as FrameManager)._client.send('Target.activateTarget', {targetId: Target.fromPage(page)._targetId});
   }
 
@@ -216,7 +216,7 @@ export class Browser extends EventEmitter {
     }
   }
 
-  async pages(): Promise<Page<Browser>[]> {
+  async pages(): Promise<Page[]> {
     const contextPages = await Promise.all(this.browserContexts().map(context => context.pages()));
     // Flatten array.
     return contextPages.reduce((acc, x) => acc.concat(x), []);

src/chromium/FrameManager.ts

@@ -62,7 +62,7 @@ type FrameData = {
 
 export class FrameManager extends EventEmitter implements frames.FrameDelegate, PageDelegate {
   _client: CDPSession;
-  private _page: Page<Browser>;
+  private _page: Page;
   private _networkManager: NetworkManager;
   private _frames = new Map<string, frames.Frame>();
   private _contextIdToContext = new Map<number, js.ExecutionContext>();
@@ -72,7 +72,7 @@ export class FrameManager extends EventEmitter implements frames.FrameDelegate,
   rawKeyboard: RawKeyboardImpl;
   screenshotterDelegate: CRScreenshotDelegate;
 
-  constructor(client: CDPSession, browserContext: BrowserContext<Browser>, ignoreHTTPSErrors: boolean) {
+  constructor(client: CDPSession, browserContext: BrowserContext, ignoreHTTPSErrors: boolean) {
     super();
     this._client = client;
     this.rawKeyboard = new RawKeyboardImpl(client);
@@ -251,7 +251,7 @@ export class FrameManager extends EventEmitter implements frames.FrameDelegate,
       this._handleFrameTree(child);
   }
 
-  page(): Page<Browser> {
+  page(): Page {
     return this._page;
   }
 
@@ -540,7 +540,7 @@ export class FrameManager extends EventEmitter implements frames.FrameDelegate,
     if (runBeforeUnload)
       await this._client.send('Page.close');
     else
-      await this._page.browser()._closePage(this._page);
+      await (this._page.browser() as Browser)._closePage(this._page);
   }
 }
 

src/chromium/Target.ts

@@ -30,25 +30,25 @@ const targetSymbol = Symbol('target');
 
 export class Target {
   private _targetInfo: Protocol.Target.TargetInfo;
-  private _browserContext: BrowserContext<Browser>;
+  private _browserContext: BrowserContext;
   _targetId: string;
   private _sessionFactory: () => Promise<CDPSession>;
   private _ignoreHTTPSErrors: boolean;
   private _defaultViewport: types.Viewport;
-  private _pagePromise: Promise<Page<Browser>> | null = null;
-  private _page: Page<Browser> | null = null;
+  private _pagePromise: Promise<Page> | null = null;
+  private _page: Page | null = null;
   private _workerPromise: Promise<Worker> | null = null;
   _initializedPromise: Promise<boolean>;
   _initializedCallback: (value?: unknown) => void;
   _isInitialized: boolean;
 
-  static fromPage(page: Page<Browser>): Target {
+  static fromPage(page: Page): Target {
     return (page as any)[targetSymbol];
   }
 
   constructor(
     targetInfo: Protocol.Target.TargetInfo,
-    browserContext: BrowserContext<Browser>,
+    browserContext: BrowserContext,
     sessionFactory: () => Promise<CDPSession>,
     ignoreHTTPSErrors: boolean,
     defaultViewport: types.Viewport | null) {
@@ -81,7 +81,7 @@ export class Target {
       this._page._didClose();
   }
 
-  async page(): Promise<Page<Browser> | null> {
+  async page(): Promise<Page | null> {
     if ((this._targetInfo.type === 'page' || this._targetInfo.type === 'background_page') && !this._pagePromise) {
       this._pagePromise = this._sessionFactory().then(async client => {
         const frameManager = new FrameManager(client, this._browserContext, this._ignoreHTTPSErrors);
@@ -128,10 +128,10 @@ export class Target {
   }
 
   browser(): Browser {
-    return this._browserContext.browser();
+    return this._browserContext.browser() as Browser;
   }
 
-  browserContext(): BrowserContext<Browser> {
+  browserContext(): BrowserContext {
     return this._browserContext;
   }
 

src/chromium/features/chromium.ts

@@ -48,7 +48,7 @@ export class Chromium extends EventEmitter {
     return target._worker();
   }
 
-  async startTracing(page: Page<Browser> | undefined, options: { path?: string; screenshots?: boolean; categories?: string[]; } = {}) {
+  async startTracing(page: Page | undefined, options: { path?: string; screenshots?: boolean; categories?: string[]; } = {}) {
     assert(!this._recording, 'Cannot start recording trace while already recording trace.');
     this._tracingClient = page ? (page._delegate as FrameManager)._client : this._client;
 
@@ -87,12 +87,12 @@ export class Chromium extends EventEmitter {
     return contentPromise;
   }
 
-  targets(context?: BrowserContext<Browser>): Target[] {
+  targets(context?: BrowserContext): Target[] {
     const targets = this._browser._allTargets();
     return context ? targets.filter(t => t.browserContext() === context) : targets;
   }
 
-  pageTarget(page: Page<Browser>): Target {
+  pageTarget(page: Page): Target {
     return Target.fromPage(page);
   }
 

src/firefox/Browser.ts

@@ -25,16 +25,16 @@ import { Page } from '../page';
 import * as types from '../types';
 import { FrameManager } from './FrameManager';
 import * as network from '../network';
-import { BrowserContext } from '../browserContext';
+import { BrowserContext, BrowserInterface } from '../browserContext';
 
-export class Browser extends EventEmitter {
+export class Browser extends EventEmitter implements BrowserInterface {
   private _connection: Connection;
   _defaultViewport: types.Viewport;
   private _process: import('child_process').ChildProcess;
   private _closeCallback: () => void;
   _targets: Map<string, Target>;
-  private _defaultContext: BrowserContext<Browser>;
-  private _contexts: Map<string, BrowserContext<Browser>>;
+  private _defaultContext: BrowserContext;
+  private _contexts: Map<string, BrowserContext>;
   private _eventListeners: RegisteredListener[];
 
   static async create(connection: Connection, defaultViewport: types.Viewport | null, process: import('child_process').ChildProcess | null, closeCallback: () => void) {
@@ -75,14 +75,14 @@ export class Browser extends EventEmitter {
     return !this._connection._closed;
   }
 
-  async createIncognitoBrowserContext(): Promise<BrowserContext<Browser>> {
+  async createIncognitoBrowserContext(): Promise<BrowserContext> {
     const {browserContextId} = await this._connection.send('Target.createBrowserContext');
     const context = this._createBrowserContext(browserContextId);
     this._contexts.set(browserContextId, context);
     return context;
   }
 
-  browserContexts(): Array<BrowserContext<Browser>> {
+  browserContexts(): Array<BrowserContext> {
     return [this._defaultContext, ...Array.from(this._contexts.values())];
   }
 
@@ -128,7 +128,7 @@ export class Browser extends EventEmitter {
     }
   }
 
-  newPage(): Promise<Page<Browser>> {
+  newPage(): Promise<Page> {
     return this._defaultContext.newPage();
   }
 
@@ -170,16 +170,16 @@ export class Browser extends EventEmitter {
     this._closeCallback();
   }
 
-  _createBrowserContext(browserContextId: string | null): BrowserContext<Browser> {
+  _createBrowserContext(browserContextId: string | null): BrowserContext {
     const isIncognito = !!browserContextId;
     const context = new BrowserContext({
-      contextPages: async (): Promise<Page<Browser>[]> => {
+      contextPages: async (): Promise<Page[]> => {
         const targets = this._allTargets().filter(target => target.browserContext() === context && target.type() === 'page');
         const pages = await Promise.all(targets.map(target => target.page()));
         return pages.filter(page => !!page);
       },
 
-      createPageInContext: async (): Promise<Page<Browser>> => {
+      createPageInContext: async (): Promise<Page> => {
         const {targetId} = await this._connection.send('Target.newPage', {
           browserContextId: browserContextId || undefined
         });
@@ -215,17 +215,17 @@ export class Browser extends EventEmitter {
 }
 
 export class Target {
-  _pagePromise?: Promise<Page<Browser>>;
-  private _page: Page<Browser> | null = null;
+  _pagePromise?: Promise<Page>;
+  private _page: Page | null = null;
   private _browser: Browser;
-  _context: BrowserContext<Browser>;
+  _context: BrowserContext;
   private _connection: Connection;
   private _targetId: string;
   private _type: 'page' | 'browser';
   _url: string;
   private _openerId: string;
 
-  constructor(connection: any, browser: Browser, context: BrowserContext<Browser>, targetId: string, type: 'page' | 'browser', url: string, openerId: string | undefined) {
+  constructor(connection: any, browser: Browser, context: BrowserContext, targetId: string, type: 'page' | 'browser', url: string, openerId: string | undefined) {
     this._browser = browser;
     this._context = context;
     this._connection = connection;
@@ -252,11 +252,11 @@ export class Target {
     return this._url;
   }
 
-  browserContext(): BrowserContext<Browser> {
+  browserContext(): BrowserContext {
     return this._context;
   }
 
-  page(): Promise<Page<Browser>> {
+  page(): Promise<Page> {
     if (this._type === 'page' && !this._pagePromise) {
       this._pagePromise = new Promise(async f => {
         const session = await this._connection.createSession(this._targetId);

src/firefox/FrameManager.ts

@@ -56,14 +56,14 @@ export class FrameManager extends EventEmitter implements frames.FrameDelegate,
   readonly rawKeyboard: RawKeyboardImpl;
   readonly screenshotterDelegate: FFScreenshotDelegate;
   readonly _session: JugglerSession;
-  readonly _page: Page<Browser>;
+  readonly _page: Page;
   private readonly _networkManager: NetworkManager;
   private _mainFrame: frames.Frame;
   private readonly _frames: Map<string, frames.Frame>;
   private readonly _contextIdToContext: Map<string, js.ExecutionContext>;
   private _eventListeners: RegisteredListener[];
 
-  constructor(session: JugglerSession, browserContext: BrowserContext<Browser>) {
+  constructor(session: JugglerSession, browserContext: BrowserContext) {
     super();
     this._session = session;
     this.rawKeyboard = new RawKeyboardImpl(session);

src/page.ts

@@ -26,7 +26,7 @@ import { Screenshotter, ScreenshotterDelegate } from './screenshotter';
 import { TimeoutSettings } from './TimeoutSettings';
 import * as types from './types';
 import { Events } from './events';
-import { BrowserContext } from './browserContext';
+import { BrowserContext, BrowserInterface } from './browserContext';
 import { ConsoleMessage, ConsoleMessageLocation } from './console';
 
 export interface PageDelegate {
@@ -69,14 +69,14 @@ export type FileChooser = {
   multiple: boolean
 };
 
-export class Page<Browser> extends EventEmitter {
+export class Page extends EventEmitter {
   private _closed = false;
   private _closedCallback: () => void;
   private _closedPromise: Promise<void>;
   private _disconnected = false;
   private _disconnectedCallback: (e: Error) => void;
   readonly _disconnectedPromise: Promise<Error>;
-  private _browserContext: BrowserContext<Browser>;
+  private _browserContext: BrowserContext;
   readonly keyboard: input.Keyboard;
   readonly mouse: input.Mouse;
   readonly _timeoutSettings: TimeoutSettings;
@@ -87,7 +87,7 @@ export class Page<Browser> extends EventEmitter {
   private _fileChooserInterceptors = new Set<(chooser: FileChooser) => void>();
   readonly _lifecycleWatchers = new Set<frames.LifecycleWatcher>();
 
-  constructor(delegate: PageDelegate, browserContext: BrowserContext<Browser>) {
+  constructor(delegate: PageDelegate, browserContext: BrowserContext) {
     super();
     this._delegate = delegate;
     this._closedPromise = new Promise(f => this._closedCallback = f);
@@ -150,11 +150,11 @@ export class Page<Browser> extends EventEmitter {
     });
   }
 
-  browser(): Browser {
+  browser(): BrowserInterface {
     return this._browserContext.browser();
   }
 
-  browserContext(): BrowserContext<Browser> {
+  browserContext(): BrowserContext {
     return this._browserContext;
   }
 

src/webkit/Browser.ts

@@ -25,15 +25,15 @@ import { Target } from './Target';
 import { Protocol } from './protocol';
 import * as types from '../types';
 import { Events } from '../events';
-import { BrowserContext } from '../browserContext';
+import { BrowserContext, BrowserInterface } from '../browserContext';
 
-export class Browser extends EventEmitter {
+export class Browser extends EventEmitter implements BrowserInterface {
   readonly _defaultViewport: types.Viewport;
   private readonly _process: childProcess.ChildProcess;
   readonly _connection: Connection;
   private _closeCallback: () => Promise<void>;
-  private readonly _defaultContext: BrowserContext<Browser>;
-  private _contexts = new Map<string, BrowserContext<Browser>>();
+  private readonly _defaultContext: BrowserContext;
+  private _contexts = new Map<string, BrowserContext>();
   _targets = new Map<string, Target>();
   private _eventListeners: RegisteredListener[];
   private _privateEvents = new EventEmitter();
@@ -86,25 +86,25 @@ export class Browser extends EventEmitter {
     return this._process;
   }
 
-  async createIncognitoBrowserContext(): Promise<BrowserContext<Browser>> {
+  async createIncognitoBrowserContext(): Promise<BrowserContext> {
     const {browserContextId} = await this._connection.send('Browser.createContext');
     const context = this._createBrowserContext(browserContextId);
     this._contexts.set(browserContextId, context);
     return context;
   }
 
-  browserContexts(): BrowserContext<Browser>[] {
+  browserContexts(): BrowserContext[] {
     return [this._defaultContext, ...Array.from(this._contexts.values())];
   }
 
-  defaultBrowserContext(): BrowserContext<Browser> {
+  defaultBrowserContext(): BrowserContext {
     return this._defaultContext;
   }
 
   async _disposeContext(browserContextId: string | null) {
   }
 
-  async newPage(): Promise<Page<Browser>> {
+  async newPage(): Promise<Page> {
     return this._defaultContext.newPage();
   }
 
@@ -136,7 +136,7 @@ export class Browser extends EventEmitter {
     }
   }
 
-  async pages(): Promise<Page<Browser>[]> {
+  async pages(): Promise<Page[]> {
     const contextPages = await Promise.all(this.browserContexts().map(context => context.pages()));
     // Flatten array.
     return contextPages.reduce((acc, x) => acc.concat(x), []);
@@ -181,13 +181,13 @@ export class Browser extends EventEmitter {
     target._didClose();
   }
 
-  _closePage(page: Page<Browser>) {
+  _closePage(page: Page) {
     this._connection.send('Target.close', {
       targetId: Target.fromPage(page)._targetId
     }).catch(debugError);
   }
 
-  async _activatePage(page: Page<Browser>): Promise<void> {
+  async _activatePage(page: Page): Promise<void> {
     await this._connection.send('Target.activate', { targetId: Target.fromPage(page)._targetId });
   }
 
@@ -210,16 +210,16 @@ export class Browser extends EventEmitter {
     await this._closeCallback.call(null);
   }
 
-  _createBrowserContext(browserContextId: string | undefined): BrowserContext<Browser> {
+  _createBrowserContext(browserContextId: string | undefined): BrowserContext {
     const isIncognito = !!browserContextId;
     const context = new BrowserContext({
-      contextPages: async (): Promise<Page<Browser>[]> => {
+      contextPages: async (): Promise<Page[]> => {
         const targets = this.targets().filter(target => target._browserContext === context && target._type === 'page');
         const pages = await Promise.all(targets.map(target => target.page()));
         return pages.filter(page => !!page);
       },
 
-      createPageInContext: async (): Promise<Page<Browser>> => {
+      createPageInContext: async (): Promise<Page> => {
         const { targetId } = await this._connection.send('Browser.createPage', { browserContextId });
         const target = this._targets.get(targetId);
         return await target.page();

src/webkit/FrameManager.ts

@@ -59,7 +59,7 @@ export class FrameManager extends EventEmitter implements frames.FrameDelegate,
   readonly rawKeyboard: RawKeyboardImpl;
   readonly screenshotterDelegate: WKScreenshotDelegate;
   _session: TargetSession;
-  readonly _page: Page<Browser>;
+  readonly _page: Page;
   private readonly _networkManager: NetworkManager;
   private readonly _frames: Map<string, frames.Frame>;
   private readonly _contextIdToContext: Map<number, js.ExecutionContext>;
@@ -68,7 +68,7 @@ export class FrameManager extends EventEmitter implements frames.FrameDelegate,
   private _mainFrame: frames.Frame;
   private readonly _bootstrapScripts: string[] = [];
 
-  constructor(browserContext: BrowserContext<Browser>) {
+  constructor(browserContext: BrowserContext) {
     super();
     this.rawKeyboard = new RawKeyboardImpl();
     this.rawMouse = new RawMouseImpl();
@@ -197,7 +197,7 @@ export class FrameManager extends EventEmitter implements frames.FrameDelegate,
       this._handleFrameTree(child);
   }
 
-  page(): Page<Browser> {
+  page(): Page {
     return this._page;
   }
 
@@ -524,6 +524,6 @@ export class FrameManager extends EventEmitter implements frames.FrameDelegate,
   async closePage(runBeforeUnload: boolean): Promise<void> {
     if (runBeforeUnload)
       throw new Error('Not implemented');
-    this._page.browser()._closePage(this._page);
+    (this._page.browser() as Browser)._closePage(this._page);
   }
 }

src/webkit/Target.ts

@@ -25,18 +25,18 @@ import { FrameManager } from './FrameManager';
 const targetSymbol = Symbol('target');
 
 export class Target {
-  readonly _browserContext: BrowserContext<Browser>;
+  readonly _browserContext: BrowserContext;
   readonly _targetId: string;
   readonly _type: 'page' | 'service-worker' | 'worker';
   private readonly _session: TargetSession;
-  private _pagePromise: Promise<Page<Browser>> | null = null;
-  _page: Page<Browser> | null = null;
+  private _pagePromise: Promise<Page> | null = null;
+  _page: Page | null = null;
 
-  static fromPage(page: Page<Browser>): Target {
+  static fromPage(page: Page): Target {
     return (page as any)[targetSymbol];
   }
 
-  constructor(session: TargetSession, targetInfo: Protocol.Target.TargetInfo, browserContext: BrowserContext<Browser>) {
+  constructor(session: TargetSession, targetInfo: Protocol.Target.TargetInfo, browserContext: BrowserContext) {
     const {targetId, type} = targetInfo;
     this._session = session;
     this._browserContext = browserContext;
@@ -84,9 +84,9 @@ export class Target {
     (this._page._delegate as FrameManager).setSession(this._session);
   }
 
-  async page(): Promise<Page<Browser>> {
+  async page(): Promise<Page> {
     if (this._type === 'page' && !this._pagePromise) {
-      const browser = this._browserContext.browser();
+      const browser = this._browserContext.browser() as Browser;
       // Reference local page variable as _page may be
       // cleared on swap.
       const frameManager = new FrameManager(this._browserContext);